Heating unit for heat-transfer fluid for a central heating installation

ABSTRACT

The invention concerns a heating unit comprising a tubular wall ( 1 ) and first and second end walls ( 2, 3 ). A first annular space ( 6 ) is located between the tubular wall ( 1 ) and a first tubular partition ( 4 ). A second annular space ( 7 ) is located between the first partition ( 4 ) and a second tubular partition ( 5 ) inside the first partition ( 4 ). An immersion heater ( 25 ) is mounted in the central channel ( 8 ) formed by the second partition ( 5 ). The second space ( 7 ) communicates with the central channel ( 8 ) near the first end wall ( 2 ) and with the first space ( 6 ) near the second end wall ( 3 ). An intake orifice ( 13 ) emerges into the first space ( 6 ) near the first end wall ( 2 ) and an outlet ( 14 ), in the second end wall ( 3 ) emerges into the central channel ( 8 ).

[0001] The invention concerns a heating unit for heat-transfer fluid fora central heating installation.

[0002] In general terms, a central heating installation comprises apipework circuit in which one or more radiators or convectors areconnected, at least one expansion device and at least one heatingstation able to heat the heat-transfer fluid which is caused tocirculate in the circuit.

[0003] The heating station of the installation can in particular be acoal, gas or oil boiler, and there also exist electric heating stations.

[0004] The aim of the present invention is to produce a central heatinginstallation in which the heating station consists of one or moreelectric heating units with a simple and compact structure, and allowingeffective and flexible functioning of the installation.

[0005] The object of the present invention is a heating unit for centralheating heat-transfer fluid. This heating unit consists of a reservoirhaving a tubular external wall, a first end wall and a second end wall,these walls delimiting a space which is in substance cylindrical. Afirst tubular internal partition and a second tubular internalpartition, substantially concentric with the tubular external wall, aremounted in the reservoir, the second internal partition having adiameter smaller than that of the first tubular partition. A firstannular space is situated between the tubular external wall and thefirst internal partition; a second annular space is situated between thefirst internal partition and the second internal partition; a centralpipe is situated inside the second internal partition. The secondannular space is in communication with the central pipe close to thefirst end wall and in communication with the first annular space closeto the second end wall. The reservoir is provided with an inlet orificeopening out in the first annular space close to the first end wall andan outlet orifice, in the second end wall, opening out in the centralpipe. At least one electric immersion heater is mounted in the centralpipe, and at least one thermostatic sensor is mounted in the reservoir.

[0006] The components making up the heating unit are preferably madefrom metal.

[0007] In particular, the tubular external wall, the first and secondend walls and the first internal partition can in particular be madefrom steel. The second internal partition can also be made from steel.According to another embodiment, this second internal partition is madefrom copper.

[0008] According to a preferred embodiment, the heating unit comprises,in the said second annular space, heat transfer elements fixed to thesaid second external partition.

[0009] These heat transfer elements can in particular consist of tworings spaced apart from one another, fixed to the said second internalpartition and disposed perpendicular to the axis thereof, these tworings having in them several holes and being connected together by meansof several metallic bars spaced apart from each other.

[0010] So as to have a large surface of contact with the heat-transferfluid which surrounds them, these metallic bars advantageously have aribbed external surface. For the same reason, these metallic bars canalso carry fins.

[0011] The said heat transfer elements are produced from a materialhaving good conductivity. The two rings between which the metallic barsare mounted can be made from steel, but are advantageously made fromcopper. The metallic bars themselves are preferably made from copper.

[0012] As already mentioned above, at least one thermostatic sensor ismounted in the reservoir. In order to provide greater safety infunctioning, it may be desirable for two thermostatic sensors to bemounted in the reservoir.

[0013] According to a particular embodiment, this thermostatic sensor orsensors are mounted in the second annular space.

[0014] According to a preferred embodiment, the first annular space isput in communication with the second annular space by means of severalopenings distributed over the periphery of the said first internalpartition, close to the second end wall.

[0015] The expression “close to the second end wall” means here that thedistance between these openings and the second end wall is appreciablysmaller than (for example no more than one quarter of) the distancebetween these openings and the first end wall.

[0016] Advantageously, a ring can be mounted in the first annular space,between the tubular external wall and the first internal partition. Thisring which, in the axial direction, has in it several holes distributedalong its periphery, is situated at an intermediate level between theinlet orifice of the reservoir and the openings which are provided inthe said first intermediate partition.

[0017] The second annular space is advantageously put in communicationwith the central pipe by the fact that a space is provided between thesecond internal partition and the first end wall.

[0018] According to a particular embodiment, the inlet orifice of thereservoir is provided in the tubular external wall, close to the firstend wall. This orifice thus opens out radially in the first annularspace.

[0019] The reservoir is preferably provided with means enabling it to befixed to a support.

[0020] According to one advantageous embodiment, two electric immersionheaters are mounted in the central pipe of the heating unit.

[0021] When the central heating installation in which the heating unitis connected is in operation, only one of these immersion heaters orboth immersion heaters may be put in operation, according tocircumstances and requirements.

[0022] Another object of the present invention is a central heatinginstallation with a heat-transfer fluid, comprising a pipework circuitin which one or more radiators or convectors are connected, at least onecirculation pump, at least one expansion device and at least one heatingunit, this installation including at least one room thermostat. At leastone heating unit according to the invention is connected in the circuitof this installation, the installation also comprising an automatedcontrol station able to receive the signals from the room thermostat orthermostats and from the thermostatic sensors of the heating unit orunits, and to control the start-up and stoppage of the functioning ofthe circulation pump or pumps and of the immersion heater or heaters ofthe heating unit or units.

[0023] The heating installation according to the invention may ifnecessary comprise two or more heating units according to the invention,these heating units then being connected in parallel in the circuit.

[0024] The heat-transfer fluid circulating in the installation ispreferably oil and, more particularly, a mineral oil specially designedfor heat transfer.

[0025] The heating unit or units connected in the circuit are preferablyable to heat the heat-transfer fluid to a temperature above 100° C.

[0026] The installation can in particular be adjusted so that thetemperature of the heat-transfer fluid (in particular oil) is limited toa temperature of between 105° C. and 110° C., at the output from theheating unit or units.

[0027] Other particularities and advantages of the invention will emergefrom the description of a heating unit according to the invention givenby way of non-limiting example, reference being made to the accompanyingdrawings, in which:

[0028]FIG. 1 is a view in axial section of the heating unit;

[0029]FIG. 2 is a transverse section of the heating unit along the lineII-II in FIG. 1; and

[0030]FIG. 3 is a transverse section of the heating unit along the lineIII-III in FIG. 1.

[0031] The heating unit consists of a reservoir having a tubularexternal wall 1, a first end wall 2 and a second end wall 3. A firsttubular internal partition 4, concentric with the external wall 1, ismounted in the reservoir. A second tubular internal partition 5, alsoconcentric with the external wall 1, is mounted inside the firstpartition 4.

[0032] A first annular space 6 is thus situated between the externalwall 1 and the first internal partition 3, and a second space 4 and thesecond internal partition 5. A central pipe 8 is situated inside thesecond tubular internal partition 5.

[0033] It should be noted that the first end wall 2 is in fact formedmainly by a ring 9 welded between the tubular elements which formrespectively the external wall 1 and the first internal partition 4 andby a ring 10 welded between the tubular elements which form respectivelythe first internal partition 4 and the second internal partition 5.

[0034] In a similar fashion, the second end wall is formed mainly by aring 11 welded between the tubular elements which form respectively theexternal wall 1 and the first internal partition 4 and by a ring 12welded between the tubular elements which form respectively the firstpartition 4 and the second internal partition 5.

[0035] The reservoir is provided with an inlet orifice which consists ofa manifold 13 welded to the external wall 1 and opening out in the firstannular space 16, close to the first end wall 2.

[0036] The reservoir is also provided with an outlet orifice which opensout from the central pipe 8 and which consists of a manifold 14 weldedin the ring 12 (which is an element making up the second end wall 3).

[0037] The second internal partition 5 carries on the outside threerings 15, 16, 17, whose external diameters are equal to (or slightlyless than) the internal diameter of the first internal partition 4. Thering 15, which is situated closest to the second end wall 3, isconnected to the ring 12 by two thimbles 18. Two thermostatic sensors 19passing through orifices provided for this purpose in the ring 12,through the said thimbles 18, are mounted in the second annular space 7.The connectors and electric wires which connect these thermostaticsensors 19 to a control station are not shown.

[0038] The other two rings 16 and 17 are spaced apart from one anotherand connected to one another by means of twelve copper bars 20 evenlyspaced apart from each other. The rings 16 and 17 each have in themtwelve holes 21 which are angularly offset with respect to the bars 20,as can be seen in FIG. 3.

[0039] Twelve holes 22 are provided in the first internal partition 4,close to the second end wall 3. These holes 22, which are evenly spacedapart on the periphery of the first tubular internal partition 4, putthe first annular space 6 in communication with the second annular space7.

[0040] A ring 23 with eight holes 24 in it is mounted between theexternal wall 1 and the first internal partition 4, at a levelintermediate between the inlet manifold 13 and the holes 22 which areprovided in the first internal partition 4. When the heating unitoperates, this ring 23 with holes 24 regularises the flow ofheat-transfer fluid which enters through the manifold 13 and whichascends towards the holes 22.

[0041] It will be noted that a space is provided between the secondinternal partition 5 and the first end wall 2, which puts the secondannular space 7 in communication with the central pipe 8.

[0042] Two electric immersion heaters 25 are situated in the centralpipe 8. These immersion heaters 25 are fixed in a base 26 which isscrewed in the ring 10, a bridge 27 providing a seal for the assembly.

[0043] Connectors 28 connect the immersion heaters 25 to electric supplycables.

[0044] Shoulders 29, 30 are intended for fixing the heating unit to anappropriate support.

[0045] When the heating unit operates, an immersion heater 25 or the twoimmersion heaters 25 are started up. During this time, the heat-transferfluid circulates in the heating unit by entering through the inlet 13,ascending in the first annular space 6, entering through the holes 22into the second annular space 7, descending in the second annular space7, and ascending again in the central pipe 8 as far as the outlet 14.

[0046] When it passes through the central pipe 8, the heat-transferfluid is in direct contact with immersion heaters 25 which raise it tothe required temperature. However, because of the thermal conductivityof the internal partitions 4 and 5, the heat-transfer fluid is alreadypreheated during its passage through the first annular space 6 and thenin particular during its passage through the second annular space 7 inwhich it comes into contact not only with the second intermediatepartition 5 but also with the heat transfer elements 16, 17 and 20.

[0047] A heating unit as described is intended to be connected in thepipework circuit of a central heating installation. In the pipeworkcircuit of such an installation there are generally connected severalradiators, at least one heating unit, at least one circulation pump andat least one expansion device. The installation also comprises at leastone room thermostat and an automated control station able to receive thesignals from the room thermostat or thermostats and the thermostaticsensors of the heating unit (or heating units), and to control thestart-up and stoppage of operation of the circulation pump (orcirculation pumps) and of the immersion heater or heaters of the heatingunit (or heating units).

[0048] The heating capacity of a heating unit obviously depends on thepower of the immersion heaters mounted in the unit. Choosing immersionheaters with appropriate power makes it possible to meet a requiredheating capacity.

[0049] It may be desirable to connect two or more heating units, inparallel, in the circuit of a central heating installation. It is alsoadvantageous for two immersion heaters to be mounted in each heatingunit.

[0050] The control station of the installation can then be programmed sothat, according to the heating requirement, one or two immersion heatersof one or more heating units would be started up. The control station isalso programmed so that the heating unit or units can function only whenthe circulation pump or pumps are operating.

[0051] The heating units according to the invention are very compact,are of very simple construction, and allow great flexibility inoperation of the installation in which they are connected.

[0052] The heat-transfer fluid which is caused to circulate in theinstallation is preferably mineral oil for the transfer of heat. Thismakes it possible in particular to heat the heat-transfer fluid to atemperature above 100° C., and this remains possible, without anyproblem, even at high altitude, in mountainous regions.

[0053] The heating unit according to the invention is a compactapparatus which contains only a small volume of heat-transfer fluid andwhich thereby has low thermal inertia.

[0054] If the radiators or convectors mounted in the installation are ofthe type with a large radiation surface and small internal volume, theinstallation overall will have low thermal inertia, which constitutes areal advantage.

1. Heating unit for heat-transfer fluid for a central heatinginstallation, characterised in that it consists of a reservoir having atubular external wall (1), a first end wall (2) and a second end wall(3), these walls (1, 2, 3) delimiting a substantially cylindrical space,a first tubular internal partition (4) and a second tubular internalpartition (5), substantially concentric with the tubular external wall(1) being mounted in the reservoir, the second internal partition (5)having a diameter smaller than that of the first internal partition (4),a first annular space (5) being situated between the tubular externalwall (1) and the first internal partition (4), a second annular space(7) being situated between the first internal partition (4) and thesecond internal partition (5), a central pipe (8) being situated insidethe second internal partition (5), the second annular space (7) being incommunication with the central channel (8) close to the first end wall(2) and in communication with the first annular space (6) close to thesecond end wall (3), the reservoir being provided with an inlet orifice(13) opening out in the first annular space (6) close to the first endwall (2), and an orifice (14), in the second end wall (3), opening outfrom the central pipe (8), at least one electric immersion heater (25)being mounted in the central pipe (8), at least one thermostatic sensor(19) being mounted in the reservoir.
 2. Heating unit according to claim1, characterised in that the tubular external wall (1), the first andsecond end walls (2, 3) and the first internal partition (4) are madefrom steel.
 3. Heating unit according to any one of the precedingclaims, characterised in that the second internal partition (5) is madefrom steel.
 4. Heating unit according to either one of claims 1 and 2,characterised in that the second internal partition (5) is made fromcopper.
 5. Heating unit according to any one of the preceding claims,characterised in that it comprises heat transfer elements situated inthe said second annular space (7) and fixed to the said second internalpartition (5).
 6. Heating unit according to claim 5, characterised inthat the said heat transfer elements consist of two rings (16, 17)spaced apart from one another, fixed to the said second internalpartition (5) and disposed perpendicular to the axis thereof, these tworings (16, 17) having several holes (21) in them and being connectedtogether by means of several metallic bars (20), spaced apart from eachother.
 7. Heating unit according to claim 6, characterised in that thesaid metallic bars (20) have a ribbed external surface.
 8. Heating unitaccording to either one of claims 6 and 7, characterised in that thesaid two rings (16, 17) fixed to the second internal partition (5) aremade from steel.
 9. Heating unit according to either of one of claims 6and 7, characterised in that the said two rings (16, 17) fixed to thesecond internal partition (5) are made from copper.
 10. Heating unitaccording to any one of claims 6 to 9, characterised in that the saidmetallic bars (20) are made from copper.
 11. Heating unit according toany one of the preceding claims, characterised in that it comprises atleast one thermostatic sensor (19) mounted in the said second annularspace (7).
 12. Heating unit according to any one of the precedingclaims, characterised in that several openings (22) distributed over theperiphery of the said first internal partition (4), close to the secondend wall (3), put the first annular space (6) and the second annularspace (7) in communication.
 13. Heating unit according to claim 12,characterised in that, perpendicular to the axis of the reservoir, aring (23) is mounted between the tubular external wall (1) and the saidfirst internal partition (4), this ring (23), with several holes (24) init distributed along its periphery, being situated at a levelintermediate between the inlet orifice (13) of the reservoir and theopenings (22) which are provided in the said first internal partition(4).
 14. Heating unit according to any one of the preceding claims,characterised in that a space is provided between the said secondinternal partition (5) and the first end wall (2), thus putting thesecond annular space (7) and the central pipe (8) in communication. 15.Heating unit according to any one of the preceding claims, characterisedin that the said inlet orifice (13) of the reservoir is provided in thetubular external wall (1).
 16. Heating unit according to any one of thepreceding claims, characterised in that the reservoir is provided withmeans (29, 30) enabling it to be fixed to a support.
 17. Heating unitaccording to any one of the preceding claims, characterised in that twoelectric immersion heaters (25) are mounted in the said central pipe(8).
 18. Central heating installation with a heat-transfer fluid,comprising a pipework circuit in which there are connected one or moreradiators or convectors, at least one circulation pump, at least oneexpansion device and at least one heating unit, the installationincluding at least one room thermostat, characterised in that at leastone heating unit according to any one of the preceding claims isconnected in the said circuit, the installation comprising an automatedcontrol station able to receive the signals from the room thermostat orthermostats and from the thermostatic sensor or sensors (19) of theheating unit or units and to control the start-up and stoppage ofoperation of the circulation pump or pumps and of the immersion heateror heaters of the heating unit or units.
 19. Central heatinginstallation according to claim 18, characterised in that two or moreheating units according to any one of claims 1 to 17 are connected inparallel in the said circuit.
 20. Central heating installation accordingto either one of claims 18 and 19, characterised in that theheat-transfer fluid is oil.
 21. Central heating installation accordingto claim 20, characterised in that the heating unit or units are able toheat the heat-transfer fluid to a temperature above 100° C.